Electric discharge lamp



July 20, 1937. L J DAVlEs 2,087,754

ELECTRIC DISCHARGE LAMP Filed Oct. 28, 1936 INVENTOR V I Leonard J. Dav: 5

BY e! ATT RNEY Patented July 20, '1937 PATENT OFFICE ELECTRIC DISCHARGE LAMP Leonard J. Davies, Rugby, England, assignor to General Electric Company, a corporation of New York Application October 28, 1936, Serial No. 108,113 In Great Britain November 1, 1935 1 Claim.

This invention relates to electric discharge lamps and more particularly to lamps in which the discharge takes place in a vapour or gas.

It has been found possible to increase the wattage input to such lamps, and thereby increase the light output and. the intrinsic brilliancy of the lamp, by operating them under artificially cooled conditions. Since for high efficiency such lamps are constructed to operate on m voltages of between 100 and 1000 or even higher, with some liquids used for cooling, and especially if water is used, electrolysis currents may flow in the water between the lead in wires to the lamp. While this is not detrimental to the light output or to the efliciency, since only a small portion of the total energy is consumed in electrolysis, it does give rise to trouble connected with the inleads to the lamp, for these are rapidly dissolved and the lamp fails through this reason. This electrolysis may be prevented by preventing access of liquid to the leads by shielding them with insulating material, but in order to cool the seals of the lamp it is desirable that the cooling liquid should have free access to the leads, or that the leads should be so designed that even if they are protected by a coating of poor thermal conductivity they can lose a good deal of heat to the liquid.

The object of this invention is to provide an improved arrangement of lead-in wire and terminals for such lamps so that they can be operated in cooling mediums in which electrolytic action may take place without the inleads being affected. The lamps to which this invention applies more specifically are, to give a typical example, constructed of quartz of approximately A" in diameter and are tubular in shape. An electrode is sealed in at each end and inleads corresponding to these electrodes extend from each end. To overcome the trouble due to electrolysis dissolving away these inlead wires, and also to provide a lamp that is readily interchangeable in a suitably designed holder I propose extending the tubular shape of the lamp at each end by tubes of copper or other high conductivity metal, or metal designed specially to reduce electrolysis. To support these extension pieces and to provide electrical and thermal conduction from the inleads to them, the space in between the inlead which passes down the centre of this tube and the inner wall of thetube is filled with a good conductor of electricity of a suitable nature, such as lead. The extension is further secured by paste if necessary. This provides a simple method of capping the lamp, in such a way that the caps can be put on with the lamp held in a jig, so that the light center is always symmetrically axial and at the correct distance from the caps, which means that the lamp can be easily 5 plugged into a holder situated in an optical device where it is important to secure the correct location of the light source. The large size of such caps furthermore mean that considerable electrolysis can take place before any serious 10 diminution in the size of the inleads occurs. Furthermore the thermal conduction along the inlead secures that the actual seals in the lamp are kept at a reasonably cool temperature and prevent trouble arising from the melting, or destruc- 15 tion by heat of the seals.

If it is desired to prevent electrolysis completely then such caps or enlarged inlead wires may be painted with an insulating paint or varnish or coated with vitreous enamels, since the large area 20 ensures suflicient cooling of the inleads even though thermal conduction is hindered by the presence of a poorly conducting varnish or enamel.

A further feature of the cap additions to the 25 lamps described above is that they can be arranged to extend over the lamp for varying distances and thus by the heat shielding they offer, afiect the electrical characteristics of the lamp, should such a control be found desirable.

In the drawing accompanying and forming" part of this specification an embodiment of the invention is shown in a side elevational, partly sectional View.

Referring to the drawing the'gaseous electric discharge device comprises an elongated tubular container l having an outside diameter of about one quarter of an inch. Said container i has electrode chambers 3 and 4, one at each end thereof. Said electrode chambers 3 and 4 have electrodes 5 and 6 mounted therein, respectively, and a quantity P2 of mercury therein in which the electrodes 5 and b are immersed for the greater part of their length. The structure and 45 operation of gaseous electric discharge lamp devices of this type are described in the co-pending application of Cornelis Bol, Willem Elenbaas, and Hendricus J. Lemmens, Serial No. 46,952, filed October 26, 1935 and assigned to the assignee of 50.

the present application. The lamp illustrated is provided with and mounted in a fluid cooling system (not shown for purposes of simplicity.)

Metal tubes 1 and 8 are mounted on said electrode chambers 3 and 4, respectively, and said 55 tubes 1 and 8 are coaxial with the current leads 9 and HI, respectively. Each of said tubes 1 and 8 are made of metal having good electrical conductivity characteristics, such as copper. The

5 space between the tubes 1 and 8 and the leads 9 and Ill, respectively, is filled with a metal body ll having good electrical conductivity characteristics, such as lead.

The advantages and modifications of lamps 10 of the above type have been pointed out above and it will be understood of course that I contemplate that still i'urther changes and modifications may be made in the device illustrated and described without departure from the spirit and 15 scope of the invention.-

lead extending therefrom, a tube of electrically conducting material surrounding said current lead, said tube being appreciably larger in diameter than said current lead and having approximately the same diameter as said container, the tapered end of said container extending into said tube and an electrically conducting solid body filling said tube.

LEONARD J. DAVIES. 

